P0121

Diagnostic Chart (Part 1 Of 2):

Diagnostic Chart (Part 2 Of 2):

Engine Controls Schematics: A/C Refrigerant Pressure Sensor, TP, MAP, ECT and IAT Sensor:

CIRCUIT DESCRIPTION
The Throttle Position (TP) sensor circuit provides a voltage signal that changes relative to throttle blade angle. The signal voltage will vary from below 1.0 volt at closed throttle to above 4.0 volts at Wide Open Throttle (WOT).

When the MAP reading is below 50 kPa the diagnostic checks for a skewed high TP sensor. When the MAP reading is above 70 kPa the diagnostic checks for a skewed low TP sensor. If the PCM detects an out of range condition, DTC P0121 will be set. The diagnostic will not run when MAP is between 50 kPa and 70 kPa.

CONDITIONS FOR RUNNING THE DTC
^ No active TP sensor circuit or MAP sensor DTC.
^ The engine is running for longer than 2 minutes.
^ The ECT sensor temperature above 75°C (167°F).
^ The MAP reading is below 50 kPa for a TP sensor skewed high.
^ The MAP reading is above 70 kPa for a TP sensor skewed low.
^ The MAP steady for 5 seconds or more.

CONDITIONS FOR SETTING THE DTC
^ The TP sensor reading is above the predicted value when the MAP is below 50 kPa.
^ The TP sensor reading is below the predicted value when the MAP is above 70 kPa.
^ The above conditions are present for 10 seconds.

ACTION TAKEN WHEN THE DTC SETS
^ The PCM will illuminate the Malfunction Indicator Lamp (MIL) during the second consecutive trip in which the diagnostic test has been run and failed.
^ The PCM will store conditions which were present when the DTC set as Freeze Frame and Failure Records data.
^ If the misfire is determined to be catalyst damaging, the PCM will flash the MIL.

CONDITIONS FOR CLEARING THE MIL/DTC
^ The PCM will turn OFF the MIL during the third consecutive trip in which the diagnostic has been run and passed.
^ The History DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction.
^ The DTC can be cleared by using a scan tool.

DIAGNOSTIC AIDS
Inspect for the following conditions:
^ Skewed MAP signal or faulty MAP sensor.
^ A skewed MAP signal may cause the PCM to incorrectly determine the TP sensor is out of range. Monitor the scan tool for an unusually low or high MAP reading. This condition can cause DTC P0121 to be set. Refer to MAP Sensor Circuit Diagnosis

IMPORTANT: Remove any debris from the connector surfaces before servicing a component. Inspect the connector gaskets when diagnosing or replacing a component. Ensure that the gaskets are installed correctly. The gaskets prevent contaminate intrusion.

^ Poor terminal connection.
Inspect the harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and faulty terminal to wire connection. Use a corresponding mating terminal to test for proper tension. Refer to Diagrams for diagnosis and repair.
^ Damaged harness.
Inspect the wiring harness for damage. If the harness inspection does not reveal a problem, observe the display on the scan tool while moving connectors and wiring harnesses related to the sensor. A change in the scan tool display may indicate the location of the fault. Refer to Diagrams for diagnosis and repair.
^ Inspect the PCM and the engine grounds for clean and secure connections.

If the DTC is determined to be intermittent, reviewing the Failure Records can be useful in determining when the DTC was last set.

TEST DESCRIPTION
The number below refers to the step number on the diagnostic table:
11. This vehicle is equipped with a PCM which utilizes an Electrically Erasable Programmable Read Only Memory (EEPROM). When the PCM is being replaced, the new PCM must be programmed.